1. Field of the Invention
This invention relates, in general, to closures for containers and more particularly to twist-open closures having an inclined frangible membrane and methods for their use.
2. Description of Related Art
Closures designed to store a consumable separate from a liquid until use are known. For example, U.S. patent application Ser. No. 10/313,575 discloses a closure including a cap, a rotatable spout, piercing structure and a sealing foil that encases a consumable material such as a tablet. The piercing structure is adapted to pierce the sealing foil and bias the foil downwardly in order to facilitate the introduction of the tablet into the liquid of a container upon rotation of the spout relative to the cap.
While the above structure is quite effective to isolate the consumable material from the contents of the container until use, in some instances a discrete sealing foil may prove undesirable. An exemplar of a prior art closure, which does not require a discrete sealing foil, is International Application Publication No. WO 01/08996 to Yu, which publication shows a spin-opening type bottle cap for separating solute and solvent. Disadvantageously, such prior bottle caps may require a significant amount of force on the part of a user to initiate opening of the bottle cap. Furthermore, prior caps are often more complicated to manufacture. For example, as very precise alignment of parts is often necessary to assembly prior caps.
What is needed is a twist-open closure that overcomes the above and other disadvantages of known closures.